Food intolerance or non-allergic food hypersensitivity is a delayed, negative reaction to a food, beverage or food additive. It can involve symptoms in one or more body organs and systems, but is not considered directly related to the immune system. Intolerance can result from the absence of specific chemicals or enzymes needed to digest a food substance, or from reactions to naturally occurring chemicals in foods. The precise distinction between food intolerance and a food allergy is often missed.

A deficiency in digestive enzymes can also cause some types of food intolerances. Dietary carbohydrate intolerances include, Lactose intolerance is a result of the body not producing sufficient lactase to digest the lactose in milk; dairy foods which are lower in lactose, such as cheese, are less likely to trigger a reaction in this case. Coeliac disease (gluten intolerance) results in damage to villi in the small intestine, which makes it difficult for the body to absorb water and nutrients from foods,and fructose intolerance.